The present invention relates to an array antenna radio communication apparatus and an array antenna radio communication method.
In a radio communication system of CDMA (Code Division Multiple Access) method, interference among various kinds of signals causes deterioration of characteristics of signals which receiving sides receive, as a plurality of communication partners transmit signals in the same frequency band.
An array antenna radio communication apparatus has been known as an apparatus for suppression of the above interference. The array antenna radio communication apparatus is a radio communication apparatus which is provided with a plurality of antennas, and may freely set directivity by adjusting each amplitude and phase of signals received at each antenna.
The array antenna radio communication apparatus adjusts the amplitude and phase of the received signals by multiplying the received signals by a weight factor (hereinafter, called as xe2x80x9cweightxe2x80x9d). The array antenna radio communication apparatus may intensely receive only signals incoming from a desired direction by adjusting the multiplying weight.
Here, multi-code transmission is sometimes used for improving a transmission rate in a mobile communication system of the CDMA method. In the mobile communication system of the CDMA method, there are some cases where desired transmission rate is not obtained on one communication channel in the case of a large amount of data, for example, when image data and voice data are required to be transmitted at the same time, as there is an upper limit in the transmission rate for one communication channel.
Then, multi-code transmission, where spread of image data and voice data is performed with different spreading codes, respectively, and, at the same time, a plurality of communication channels are used for simultaneous transmission of the image data and the voice data, is used. As described above, desired transmission rate may be obtained even in the case of large amounts of data, as data is transmitted, using a plurality of communication channels at the same time in the multi-code transmission.
However, there is a following problem, when a conventional array antenna radio communication apparatus is applied for the CDMA radio communication system in which the multi-code transmission is performed.
That is, the array antenna radio communication apparatus obtains reception weights respectively for demodulation data obtained after despreading of the received signals with a plurality of different spreading codes in the case where the multi-code transmission is performed. All the reception weights obtained as described above are obtained from a signal transmitted from one communication partner. Therefore, all the reception weights naturally have the same value, by which the directivity is formed in the direction of a position where the communication end is located.
However, a plurality of reception weights sometimes have the different value, respectively, as there are caused different errors respectively in a plurality of reception weights by noise, differences in power among signals of each channel, differences in correlation values depending on the difference in the spreading codes, and so on.
An object of the present invention is to provide an array antenna radio communication apparatus and an array antenna radio communication method, capable of improving a reception quality by setting values of the reception weights for a plurality of signals transmitted from the same direction on a plurality of channels to the same value.
In order to achieve the above object, in the present invention, the same directional pattern is formed for all signals transmitted from the same direction by setting values of reception weights for a plurality of signals, which are transmitted on a plurality of channels from the same direction, to a value of an accurate reception weight. Thereby, the reception quality may be improved.